<!DOCTYPE html>
<html>
  <head>
      <style>
    body {
      margin: 0;
    }
        .before {
      width: 100px;
      height: 100px;
      background-color: red;
    }
      </style>
  </head>
  <body>
    <div class="before">
    </div>
  </body>
</html>
